Electrical submersible well pumps are often used to pump liquids from hydrocarbon producing wells. A typical ESP includes a pump driven by an electrical motor. Production tubing, which comprises pipes having threaded ends secured together, supports the ESP in most installations. The pump normally pumps well fluid into the production tubing. A power cable extends alongside the production tubing to the motor for supplying power. Installing and retrieving the ESP requires a workover rig to pull the production tubing.
In other installations, coiled tubing supports the ESP. The coiled tubing comprises a continuous length or segment of steel tubing that can be wound on a large reel at the surface before deploying and after retrieving. A power cable with power conductors for supplying power to the motor extends through the coiled tubing. The pump discharges well fluid up the annulus surrounding the coiled tubing. A coiled tubing installation allows the ESP to be installed and retrieved without the need for a workover rig.
A connector secures the coiled tubing to the upper end of the motor, which is located above the pump. The motor is filled with a dielectric lubricant for lubricating the bearings. A seal section between the motor and the pump has a bellows or flexible bag that contracts and expands to equalize the pressure of the dielectric lubricant with the well fluid pressure surrounding the motor. The connector also has electrical connections to connect the motor wires with the conductors in the power cable. In the prior art, the connector will have features to reduce the chance for well fluid that might leak into the connector from migrating down into the motor. At least some prior art connectors are filled with a dielectric fluid that immerses the electrical connections in the connector. A bellows or check valve may have been used to accommodate thermal expansion of the dielectric fluid in the connector.
Also, some prior art connectors have the ability to part in the event the ESP becomes stuck in the well, enabling the operator to retrieve the coiled tubing then run back in with a fishing string to engage and pull the stuck ESP from the well.